It is more of a culture thing than a off beat thing. Some language communities care more about backwards compatibility than others, e.g. one famous example that

It is more of a culture thing than a off beat thing. Some language communities care more about backwards compatibility than others, e.g. one famous example that is brought often here is Common Lisp and that is certainly far from mainstream. On the other hand while JavaScript-the-language is indeed backwards compatible, the culture around it is anything but - and that is despite JavaScript being as mainstream as it can get.